This invention relates to a stacking apparatus for a sewing machine, and more particularly to a stacking apparatus which is adapted to stack workpieces which are, for example, one-sidedly thicker as a result of sewing buttons to the workpiece on one side thereof or buttonhole stitching the same.
As is well known to those skilled in the art, there has in the past been proposed a workpiece stacker of the type shown in FIG. 4, which is arranged to dispose a workpiece carrier b under a work-table a of a sewing machine. The workpiece carrier b is swingably rotated about a pivot b1 provided at the lower end thereof. An arm g is so mounted as to be swung about the pivot b1 to move a horizontal member b2 and horizontally supports at its forward end a workpiece draper e in parallel with a horizontal member b2. Reference characters c, d designate two cylinders for pivoting the workpiece carrier b and the arm g, respectively. Reference characters f, h, and i denote a workpiece feeding conveyor, a button and a sewn workpiece, respectively.
An arrangement of this type makes the workpiece carrier b swingable about the pivot b1 in the direction of an arrow A to allow the horizontal member b2 of the workpiece carrier b to press the neighborhood of the lower end of the sewn workpiece suspended from the work-table a of the sewing machine against the one side of the workpiece draper e. The workpiece carrier b and workpiece draper e hold the lower end of the workpiece therebetween and are pivoted about he pivot b1, thus moving the workpiece carrier b in the direction of the work-table (an arrow B) upon passing through a position where the workpiece is suspended. The workpiece i is further fed by the conveyor f and stacked on the draper e. Thereafter, the carrier b and draper e are returned to a position shown by a solid line to be ready for the next stacking of the workpiece.
When used in a button sewing machine, the conventional workpiece stacker is likely to tend to render thicker the side of the workpieces to which buttons are applied than the other side edge thereof to which no button is applied, thereby failing to keep the workpieces in a stack. This will require additional labor since the workpieces should be re-stacked when conveyed to the next process step. Another disadvantage derived from the workpiece stacker is that the number of the workpieces to be stacked is limited due to the thickness of the button sewed or buttonhole stitched workpieces.
As shown in FIG. 5, the stack of the workpieces takes a shape of a truncated pyramid as the workpieces are successively stacked to provide a trapezoid, at the top of the stack, whose base side length D is greater than the side C opposite thereto and which is placed at an angle with the horizontal. This will prevent the carrier from performing its function and narrow the space between the work-table a and the carrier so that the volume of the stack may be limited.